BCAA

BCAAs are the three branched-chain amino acids — leucine, isoleucine and valine (often in a 2:1:1 ratio). Leucine switches on muscle-protein synthesis, while isoleucine and valine support energy and help reduce fatigue.

Usually 5–10 g is mixed with water and sipped during training — a tasty drink also helps you drink more. Many BCAAs include electrolytes, and with almost no sugar or calories they're handy when cutting.